1. Field of the Invention
The invention relates to an electrochemical storage cell of the alkali metal and chalcogen type with a least one anode space for receiving the anolyte, and a cathode space for receiving the catholyte, which spaces are separated from each other by an alkali ion-conducting solid electrolyte and are confined, at least in regions, by a metallic housing.
2. Description of the Prior Art
Such rechargeable electrochemical storage cells with a solid electrolyte are highly suitable for constructing storage batteries of high energy and power density. The solid electrolytes which are used in the alkali/chalogen storage cells and are made, for instance, of beta-aluminum oxide, are distinguished by the property that the partial conductivity of the mobile ion is very high and the partial conductivity of the electrons is smaller by several powers of ten. By the use of such solid electrolytes for the construction of electrochemical storage cells, there is achieved practically no self-discharge, since the electron conductivity is negligible and the reactive substances cannot get through the solid electrolyte as neutral particles.
A specific example for such rechargeable electrochemical storage cells are those based on sodium and sulfur, and the solid electrolyte is made of beta-aluminum oxide. One advantage of these electrochemical storage cells is that no electrochemical side reactions occur during charging. The reason for this is that only one kind of ions can get through the solid electrolyte. The current yield of such a sodium/sulfur storage cell is therefore nearly 100 percent. In these electrochemical storage cells, the ratio of the energy content to the total weight of such a storage cell is very high as compared to lead storage batteries, since the reactive substances are light and much energy is liberated during the electrochemical reaction. Electrochemical storage cells of the sodium-and-sulfur type therefore have considerable advantages over conventional storage cells such as lead storage cells.
Electrochemical storage cells of this type have the disadvantage that the destruction of the solid electrolyte can come about if an excessively high voltage is applied to the storage cells. Aging or mechanical damage of the solid electrolytes of such storage cells also can lead to breakage thereof. As a consequence, the sodium and sulfur flow together and can react directly with each other. A great temperature rise within the storage cell can come about so that, in the extreme cases, the destruction of the metallic cell housing or of the entire storage cell due to an explosion can come about.